The present invention relates to a method of backing carpets, and to carpets backed by the method. More particularly, the present invention relates to a method of backing carpets to be laid chiefly on indoor floorboards or various floor coverings, and to carpets backed by the method.
Heretofore, the backing of carpets has been conducted in the following manner: after treating the back of carpets, for example, by a method in which sols prepared by mixing vinyl chloride resins and plasticizers are applied, and cured by heating, a method in which latex compounds are applied, and dried by heating, a method in which mixtures of aqueous emulsions and thermoplastic resin powders are applied, and dried by heating, a method in which thermoplastic resin powders are sprinkled, and melted by heating, a method in which melted thermoplastic resins extruded from extruders are applied, or a method in which thermoplastic resin sheets are laid, and melted by heating, fabrics such as non-woven fabrics are laminated to the treated surfaces of the carpets.
However, the above-described conventional methods for treating carpets to be backed have the following drawbacks. Vinyl chloride resins, which are usually used for backing tile carpets (square carpets), emit dioxin and chlorine gas when carpets backed by using these resins are incinerated as wastes after use. In addition, plasticizers for use with vinyl chloride resins include DOP, DBP, etc., which can pollute the environment. Further, in the case where thick fabrics such as non-woven fabrics are laminated to the back of carpets after applying thereto latices or aqueous emulsions, the resulting laminates show poor air permeability, so that the latices or aqueous emulsions applied cannot be dried in a short time. This makes the production rate lower, and the productivity is thus decreased. In the case of hot melt coating, there is a limitation on the width of carpets to be treated; this is one cause of increase in production cost. Moreover, powders tend to scatter during operation, so that the use of powders is unfavorable from the viewpoint of working environment.
An object of the present invention is to provide a practical method of backing a carpet, using a polymeric emulsion compound that is safe and easy to handle, capable of overcoming the drawbacks with the conventional methods using aqueous systems, that is, capable of attaining rapid drying and curing of the emulsion compound even when the emulsion compound is applied to a thickness of as great as 1 mm or more. Another object of the present invention is to provide a carpet backed by this method.
The present invention provides a method of backing a carpet, comprising the steps of applying an aqueous emulsion composition described below to the back of a carpet, laminating a fabric to the composition-applied surface of the carpet, and thermally curing and then drying the composition applied; and a carpet backed by this method.
Aqueous Emulsion Composition
An aqueous emulsion composition for use in the present invention comprises:
a high-solid-content emulsion compound comprising:
(A) 100 parts by weight (solid basis) of at least one latex or emulsion selected from the group consisting of styrene-butadiene copolymer latices, acrylic resin emulsions, ethylene-vinyl acetate copolymer emulsions, acrylonitrile-butadiene copolymer latices, urethane resin emulsions, and natural rubber latices,
(B) 0.3 to 2 parts by weight of a dispersing agent,
(C) 0.5 to 5 parts by weight of a crosslinking agent,
(D) 0.1 to 4 parts by weight of an anti-foaming agent, and
(E) 100 to 600 parts by weight of at least one powdered filler selected from the group consisting of calcium carbonate, aluminum hydroxide, silica sand, and barium sulfate; and
(F) 0.5 to 30 parts by weight of a polyisocyanate compound having reactive isocyanate group, wherein the polyisocyanate compound is added to the high-solid-content emulsion compound.
According to the present invention, the aqueous emulsion composition is obtained, preferably just before use, by adding the polyisocyanate compound, which serves as a curing agent, to the high-solid-content emulsion compound, and used for backing a carpet. The polyisocyanate compound reacts with water contained in the emulsion compound to cure the aqueous emulsion composition, so that the aqueous emulsion composition applied is dried quickly. Therefore, even when the aqueous emulsion composition is applied to the back of a carpet to a thickness of as great as 1 mm or more, high productivity can be attained regardless of the thickness of a fabric such as a non-woven fabric laminated to the back of the carpet. A backed carpet can thus be inexpensively obtained. Moreover, even when the aqueous emulsion composition is applied to the back of a carpet to a thickness of as great as 1 mm or more, the obtained carpet shows elasticity without using any plasticizer. In addition, when the obtained carpet is burned, it scarcely fumes and it emits only small amounts of toxic gasses. A backed carpet favorable from the viewpoint of environmental pollution can thus be successfully obtained by the method of the invention.
Aqueous Emulsion Composition
Component (A)
Component (A) for use in the aqueous emulsion composition of the present invention is at least one base rubber emulsion selected from the group consisting of styrene-butadiene copolymer latices, acrylic resin emulsions, ethylene-vinyl acetate copolymer emulsions, acrylonitrile-butadiene copolymer latices, urethane resin emulsions, and natural rubber latices.
Component (A) is used in the aqueous emulsion composition of the invention as a base rubber. This component serves as a binder and as an anchorage for carpet yarn, and imparts anti-folding properties and elasticity to a carpet.
Styrene-butadiene copolymer latices useful for component (A) are, for instance, SBR latices obtainable by copolymerization of 15 to 85% by weight, preferably 25 to 50% by weight of styrene with 85 to 15% by weight, preferably 75 to 50% by weight of butadiene, having glass transition temperatures of xe2x88x9260 to xe2x88x9210xc2x0 C., preferably xe2x88x9250 to xe2x88x9215xc2x0 C. The SBR latices may be carboxy-modifed ones obtained by copolymerizing the above two monomers and not more than 8% by weight, preferably about 0.5 to 5% by weight of, for example, acrylic, methacrylic, itaconic, phthalic or maleic acid. The SBR latices may also be amide-modified ones obtained by copolymerizing the above two monomers and (meth)acrylic amide or the like.
Acrylic resin emulsions that are used as component (A) are preferably acrylic ester-methacrylic acid-styrene copolymer emulsions having glass transition temperatures of xe2x88x9260 to xe2x88x9210xc2x0 C., preferably xe2x88x9250 to xe2x88x9215xc2x0 C., obtained by emulsion-copolymerizing acrylic esters, methacrylic acid, and styrene. Examples of acrylic esters useful herein include those ones having 1 to 4 carbon atoms, such as methyl acrylate, hydroxyethyl acrylate and butyl acrylate. The acrylic ester/methacrylic acid/styrene ratio for copolymerization is (40 to 90% by weight)/(60 to 10% by weight)/(10 to 60% by weight), preferably (50 to 80% by weight) (50 to 20% by weight) (10 to 30% by weight) The acrylic resin emulsions may be carboxy-modifed ones obtained by copolymerizing the above three monomers and not more than 8% by weight, preferably about 0. 5 to 5% by weight of, for example, acrylic, methacrylic, itaconic, phthalic or maleic acid. The acrylic resin emulsions may also be amide-modified ones obtained by copolymerizing the above three monomers and (meth)acrylic amide or the like.
Ethylene-vinyl acetate emulsions that can be used as component (A) are EVA emulsions obtainable by copolymerization of 10 to 40% by weight, preferably 15 to 30% by weight of ethylene with 90 to 60% by weight, preferably 85 to 70% by weight of vinyl acetate, having glass transition temperatures between xe2x88x9235xc2x0 C. and +10xc2x0 C., preferably between xe2x88x9230xc2x0 and 0 Cxc2x0.
Acrylonitrile-butadiene copolymer latices useful for component (A) are, for example, NBR latices obtained by copolymerizing 15 to 50% by weight, preferably 20 to 45% by weight of acrylonitrile with 85 to 50% by weight, preferably 80 to 55% by weight of butadiene, having glass transition temperatures between xe2x88x9260xc2x0 C. and xe2x88x9210xc2x0 C., preferably between xe2x88x9250xc2x0 C. and xe2x88x9215xc2x0 C. The NBR latices may be carboxy-modifed ones obtained by copolymerizing the above two monomers and not more than 8% by weight, preferably about 0.5 to 5% by weight of, for example, acrylic, methacrylic, itaconic, phthalic or maleic acid. The NBR latices may also be amide-modified ones obtained by copolymerizing the above two monomers and (meth) acrylic amide or the like.
Urethane resin emulsions that are used as component (A) are those ones obtained by dispersing urethane elastomers in water, having glass transition temperatures ranging from xe2x88x9260 to +10xc2x0 C., preferably from xe2x88x9250 to 0xc2x0 C.
Examples of natural rubber latices that can be used as component (A) include commercially available natural rubber latices, natural rubber latices graft-polymerized with styrene, methyl methacrylate, or the like, low-ammonia natural rubber latices, and low-protein or deprotenized natural rubber latices produced by repeatedly conducting dilution with water and centrifugal separation.
The above-described component (A), base rubber emulsion (latex), should be a high-solid-content emulsion (latex) having a solid content of preferably 45% by weight or more, more preferably 55% by weight or more, particularly 60 to 70% by weight. When component (A) having a solid content of less than 45% by weight is used, the resulting aqueous emulsion composition cannot have a high solid content. Such a composition cannot be rapidly dried, and thus decreases the productivity.
(B) Dispersing Agent
In the aqueous emulsion composition of the present invention, the dispersing agent, component (B), acts to uniformly disperse a filler, and to properly maintain the viscosity of the composition.
Examples of dispersing agents that can be used as component (B) include inorganic dispersing agents such as tripolyphosphates and pyrophosphates, and polymeric dispersing agents such as polycarboxylates and formalin-condensed naphthalenesulfonates. Of these, inorganic dispersing agents are preferred.
Component (B) is used in an amount of 0.3 to 2 parts by weight, preferably 0.5 to 1.5 parts by weight for 100 parts by weight (solid basis) of component (A). The use of less than 0.3 parts by weight of component (B) is not enough to uniformly disperse a filler. On the other hand, when component (B) is used in an amount of more than 2 parts by weight, the aqueous emulsion composition finally obtained cannot keep its viscosity; the composition thus undergoes separation, and a filler settles.
(C) Crosslinking Agent
In the aqueous emulsion composition of the present invention, the crosslinking agent, component (C), acts to cross-link component (A), thereby imparting increased strength, elasticity and improved aging resistance to a carpet.
Examples of crosslinking agents that can be used as component (C) include sulfur and zinc oxide.
Component (C) is used in an amount of 0.5 to 5 parts by weight, preferably 1 to 3 parts by weight for 100 parts by weight (solid basis) of component (A). The use of less than 0.5 parts by weight of component (C) is not enough to satisfactorily impart strength, elasticity and aging resistance to a carpet. On the other hand, when more than 5 parts by weight of component (C) is used, a carpet backed by using the resulting emulsion composition is stiff and non-elastic, and readily broken.
(D) Anti-foaming Agent
In the aqueous emulsion composition of the present invention, the anti-foaming agent, component (D), acts to prevent foaming that can occur during preparation of the emulsion composition, and foaming that can occur in the process of the backing of a carpet.
Examples of anti-foaming agents that can be used as component (D) include mineral oil nonionic surface-active agents; silicone antifoamers such as polydimethylsiloxane oils, and ethylene-oxide- or propylene-oxide-modified dimethyl silicones and emulsions thereof; mineral oils; and alcoholic antifoamers such as acetylene alcohol.
Component (D) is used in an amount of 0.1 to 4% by weight, preferably 0.3 to 3% by weight for 100 parts by weight (solid basis) of component (A). The use of less than 0.1 parts by weight of component (D) is not enough to fully obtain the anti-foaming effect. On the other hand, the use of more than 4 parts by weight of component (D) brings about cissing crawling, so that a carpet backed by using the resulting emulsion composition cannot have good appearance.
(E) Filler
Component (E) is one or more powdered fillers selected from the group consisting of calcium carbonate, aluminum hydroxide, silica sand, and barium sulfate.
The powdered filler is used as an extender for the purposes of increasing the solid content of the aqueous emulsion composition, and making a carpet weighty.
Component (E) is used in an amount of 100 to 600 parts by weight, preferably 150 to 500 parts by weight for 100 parts by weight (solid basis) of component (A). When component (E) is used in an amount of less than 100 parts by weight, it cannot fully serve as an extender, and cannot make a carpet weighty. On the other hand, when component (E) is used in an amount of more than 600 parts by weight, a carpet backed by using the resulting emulsion composition has an excessively heavy weight per unit area, and is poor in rubber elasticity.
The above-enumerated powdered fillers, component (E), can be used either singly or as a mixture of two or more members.
(F) Polyisocyanate Compound having Reactive Isocyanate Group (Curing Agent)
In the aqueous emulsion composition of the present invention, the polyisocyanate compound having reactive isocyanate group, component (F), serves as a curing agent. The polyisocyanate compound reacts with water according to, for instance, the following reaction scheme, thereby curing the emulsion composition:
2RNCO+H2Oxe2x86x92RNHCONHR+CO2
wherein R represents an organic group. Water contained in the emulsion composition is thus consumed as the reaction proceeds, so that the emulsion composition applied to the back of a carpet is dried rapidly.
Examples of polyisocyanate compounds having reactive isocyanate group, component (F), for use in the present invention include diisocyanate compounds such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tetramethyl-xylylene diisocyanate, 4,4xe2x80x2-biphenyl diisocyanate, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-biphenyl diisocyanate, 4,4xe2x80x2-diphenylmethane diisocyanate, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-diphenylmethane diisocyanate, triphenylmethane diisocyanate, naphthalene diisocyanate, isophorone diisocyanate, cyclohexylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate and hexamethylene diisocyanate; triisocyanate compounds such as biphenyl triisocyanate, diphenylmethane triisocyanate, triphenylmethane triisocyanate and naphthalene triisocyanate; and polymers thereof.
A polyisocyanate compound in the form of a prepolymer having at its terminal end reactive isocyanate group, obtainable by reaction between a polyisocyanate compound having reactive isocyanate group and a polyamine compound, a polyhydric alcohol, a polyol compound or the like can also be used as component (F) Examples of polyamine compounds that can be used for the above reaction include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenehexamine, pentaethylenehexamine, cyclohexylenediamines, isophoronediamines, phenylenediamines, tolylenediamines, xylylenediamines, diphenylmethanediamines, triphenylmethanepolyamines, piperazine, and aminoethyl piperazine.
Examples of polyhydric alcohols useful for the above-described reaction include ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, hexamethylene glycol, diethylene glycol, triethylene glycol, glycerin, hexanetriol, trimethylolpropane, pentaerythritol, and sorbitol.
Examples of polyol compounds useful for the above-described reaction include polyether polyol compounds that can be obtained by addition polymerization reaction between the above-enumerated polyhydric alcohols and alkylene oxides such as ethylene oxide and propylene oxide; polyester polyol compounds that can be obtained by condensation reaction between the above polyhydric alcohols and polybasic acids such as maleic acid, succinic acid, adipic acid, sebacic acid, tartaric acid, terephthalic acid, and isophthalic acid; polyester polyol compounds obtainable by ring opening polymerization of lactones such as xcex5-caprolactone and xcex3-valerolactone; epoxypolyol compounds obtained by reacting epoxy resins having epoxy groups at both terminal ends with alkanolamines such as monoethanolamine and diethanolamine; homo- or co-polymers of hydroxyl group-containing polymerizable monomers such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate and trimethylolpropane (meth)acrylic monoesters; copolymers of the above-described hydroxyl group-containing polymerizable monomers and other copolymerizable monomers such as (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, (meth)acrylonitrile, styrene and xcex1-methylstyrene; and castor oil and its derivatives.
The above-enumerated polyisocyanate compounds, component (F), can be used either singly or as a mixture of two or more members.
Component (F) is used in an amount of 0.5 to 30 parts by weight, preferably 2 to 20 parts by weight for 100 parts by weight (solid basis) of component (A). When less than 0.5 parts by weight of component (F) is used, the aqueous emulsion composition finally obtained cures slowly. On the other hand, when more than 30 parts by weight of component (F) is used, the resulting aqueous emulsion composition cures too quickly; such a composition is poor in workability because it cures even before application.
To obtain the aqueous emulsion composition of the invention, component (F) can be added to the high-solid-content emulsion compound prepared by mixing the above-described components (A) to (E), at any point of time between the completion of preparation of the emulsion compound and the application of the aqueous emulsion composition. It is however desirable to make the aqueous emulsion composition just before application, by adding component (F) to the high-solid-content emulsion compound, and stirring the mixture.
Other Additives (Antioxidants, etc.)
In addition to the above-described components (A) to (F), pigments such as carbon black, red oxide and organic colorants, antioxidants, surface-active agents, thickeners, preservatives, and the like may optionally be incorporated into the aqueous emulsion composition of the present invention.
Preparation of Aqueous Emulsion Composition of the Invention
The aqueous emulsion composition for use in the method of the present invention is obtained, before application, by adding the above-described polyisocyanate compound, component (F), to the high-solid-content emulsion compound having a solid content of 75% by weight or more, prepared by mixing the above-described components (A) to (E).
The high-solid-content emulsion compound is herein required to have a solid content of as high as 75% by weight or more, preferably 80 to 87% by weight. When an emulsion compound having a solid content of less than 75% by weight is used, the resulting aqueous emulsion composition has a high water content. It is therefore necessary to use an increased amount of the polyisocyanate compound, component (F), to cure the aqueous emulsion composition, and the production cost is thus increased. In addition, since such a composition readily foams, it is poor in both performance and drying characteristics.
The mixing of components (A) to (E), and that of the high-solid-content emulsion compound containing components (A) to (E) and the polyisocyanate compound, component (F), can be conducted with a mixer such as a line blender, a kneader, or a blender. In either case, the mixing temperature is generally from 5 to 35xc2x0 C.
Method of Backing Carpets
According to the method of the present invention, the aqueous emulsion composition of the invention obtained by adding component (F), which serves as a curing agent, to the high-solid-content emulsion compound containing the above-described components (A) to (E) is applied to the back of a carpet; a fabric is laminated to the composition-applied surface of the carpet; and the emulsion composition applied is thermally cured and then dried. With this method, the time required for the drying step is drastically shortened, and a carpet to which a fabric is laminated through a strong cured film is successfully obtained.
Typical examples of carpets that can be obtained by the method of the invention are tile carpets which have fiber-made working surfaces, which are square in shape, which are backed by strong reinforcing layers and which are set on floors by being joined together.
Examples of fibers useful for producing such tile carpets include polyester fibers, acrylic fibers, polyamide fibers, wool, and polypropylene fibers. The tile carpets generally have thicknesses of approximately 5 to 10 mm, preferably about 6 to 9 mm, and masses of pile per unit of approximately 2,000 to 6,000 g/m2, preferably about 3,000 to 5,000 g/m2.
Besides the tile carpets, heavy-weight carpets such as contract carpets for use in hotels, department stores, etc., residential carpets for use in apartment houses, individual homes, etc., and center rugs are also included in the carpets obtainable by the method of the present invention.
Examples of fibers useful for producing raw fabrics for the above-mentioned heavy-weight carpets include polyester fibers, acrylic fibers, polyamide fibers, wool, and polypropylene fibers. Such raw fabrics generally have thicknesses of approximately 3 to 13 mm, preferably about 5 to 10 mm, and masses of pile per unit of approximately 600 to 2,000 g/m2, preferably about 800 to 1,500 g/m2.
On the other hand, fabrics to be laminated to the back of carpets are, for example, non-woven fabrics, knitted webs (meshes), and woven fabrics. Of these, non-woven fabrics are preferred.
Examples of materials for these fabrics include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as nylon 6 and nylon 6,6, regenerated fibers such as rayon, semi-synthetic fibers such as cellulose acetate, natural fibers such as cotton and wool, and inorganic fibers such as glass fibers and carbon fibers.
The above-described non-woven fabrics are generally produced by such a method as spun bonding, a papermaking process, or needle punching.
In the present invention, the basis weights of non-woven fabrics to be laminated to tile carpets are generally about 20 to 200 g/m2, preferably about 50 to 150 g/m2, and those of non-woven fabrics to be laminated to raw fabrics for heavy-weight carpets are generally about 150 to 1,500 g/m2, preferably about 300 to 1,000 g/m2.
In the method of backing carpets according to the present invention, the polyisocyanate compound (F), which serves as a curing agent, is added to the high-solid-content emulsion compound containing, as main components, components (A) to (E) to obtain the aqueous emulsion composition of the invention. Since the polyisocyanate compound reacts with water, water contained in the emulsion compound is consumed as the reaction proceeds. Therefore, heating at 160xc2x0 C. for approximately 3 minutes, for example, is enough to obtain a cured and dried film (a laminating layer) having high strength, capable of withstanding practical use. The time required for the drying step can thus be drastically shortened.
The following is one example of the method of backing carpets according to the present invention. However, the present invention is not limited to the following example in any way.
Just before application, the above-described polyisocyanate compound, component (F), is added to a high-solid-content emulsion compound prepared by mixing the above-described components (A) to (E), having a solid content of 75% by weight or more, and the mixture is stirred by using a mixer such as a line blender to obtain an aqueous emulsion composition of the invention. The aqueous emulsion composition obtained is applied to the back of a tile carpet at a thickness of 1 to 3 mm, or to the back of a raw fabric for a heavy-weight carpet at a thickness of 0.5 to 1 mm. A fabric such as a non-woven fabric is then laminated to the composition-applied surface of the tile carpet or raw fabric. This laminate is passed through a hot-air dryer at a temperature between 100xc2x0 C. and 180xc2x0 C., preferably between 150xc2x0 C. and 170xc2x0 C. over a period of time of 1 to 20 minutes, preferably 3 to 15 minutes to thermally cure and then dry the emulsion composition applied, thereby obtaining a carpet backed by the fabric.
The advantages of the method of backing carpets according to the present invention over the conventional methods are as follows.
(1) When conventional tile carpets backed by fabrics through the use of sols prepared by mixing vinyl chloride resins and plasticizers are incinerated as wastes after use, they emit dioxin and chlorine gas. On the contrary, tile carpets backed by the method of the present invention, using the aqueous emulsion compositions emit neither chlorine gas nor dioxin when incinerated because the emulsion compositions contain no chlorine.
(2) One of the conventional methods of backing heavy-weight carpets is as follows: compositions prepared by mixing aqueous emulsions with thermoplastic resin powders such as polyethylene powder are applied to the back of raw fabrics for heavy-weight carpets; fabrics such as non-woven fabrics are laminated to the composition-applied surfaces of the raw fabrics; and the compositions applied are then dried. In such a method, the compositions applied cannot be dried in a short time, so that the production rate cannot be increased. In addition, there is a limitation on the thickness of the fabrics such as non-woven fabrics to be laminated. On the other hand, the method of the present invention can attain increased productivity regardless of the thickness of the fabrics such as non-woven fabrics to be laminated. Backed carpets can thus be inexpensively obtained by the method of the invention.
(3) In the conventional method in which fabrics such as non-woven fabrics are laminated to the back of carpets after applying thereto melted thermoplastic resins extruded from extruders, or after sprinkling thereon powders, and melting them by heating, or after placing thereon thermoplastic resin sheets, and melting them by heating, there is a limitation on the width of carpets to be backed. It is therefore impossible to produce wide carpets, and the carpets backed by these methods are costly. Further, powders tend to scatter to make the working environment worse. According to the method of the present invention, carpets or raw fabrics having any width can be backed, and improved productivity can be attained regardless of the thickness of fabrics to be laminated for backing. Backed carpets can thus be inexpensively produced by the method of the invention. In addition, the aqueous emulsion compositions of the invention are safe and easy to handle, and can readily be applied.
According to the present invention, the aqueous emulsion composition obtained by adding the polyisocyanate compound, which serves as a curing agent, to the high-solid-content emulsion compound is applied to the back of a carpet. Therefore, the time needed for thermally curing and drying the emulsion composition applied becomes much shorter than the time required for drying emulsions that are used in the conventional methods. The time required for the drying step can thus be drastically shortened.
Further, a carpet backed by the method of the present invention scarcely fumes, and it emits only small amounts of toxic gases when burned, as compared with a carpet backed by the conventional method using vinyl chloride resin sols. Backed carpets obtained by the method of the invention are thus very favorable from the viewpoint of environmental pollution.
Furthermore, the aqueous emulsion compositions of the present invention are safe, easy to handle and excellent in application properties as compared with emulsions for use in the conventional methods.